CN104143180A - Method for conducting non-uniformity correction on sub-pixel images through multi-linear-array time difference scanning - Google Patents

Abstract

The invention provides a method for conducting non-uniformity correction on sub-pixel images through multi-linear-array time difference scanning. The method includes the steps that (1) a multi-linear-array time difference scanning detection device is constructed; (2) each linear array detector conducts scanning imaging in the scanning direction according to a sampling interval, Nt groups of image data are obtained through each time of imaging, and the step (3) is conducted immediately; (3) the Nt groups of image data of each linear array detector are processed to form a frame detection image; (4) the frame detection images are spliced to obtain the two sub-pixel images; (5) cross splicing is conducted on the two sub-pixel images according to columns to form an image Ip1; (6) an image Ip2 processed through column-wise non-uniformity correction is obtained; (7) two sub-pixel images processed through column-wise non-uniformity correction are rebuilt; (8) the two sub-pixel images are rotated by 90 degrees in the same direction to obtain an image Ip3; (9) two sub-pixel images processed through line-direction non-uniformity correction are rebuilt; (10) the two sub-pixel images are rotated by 90 degrees in the reverse directions.

Description

A kind of multi-thread row moveout scan subpixel image nonuniformity correction method

Technical field

The invention belongs to image processing field, relate to a kind of multi-thread row moveout scan subpixel image nonuniformity correction method.

Background technology

The application of remote sensing images is more and more extensive, but owing to being subject to the impact of the composite factors such as sensitive detection parts self, process conditions, extraneous input, the first output responsibility of each detection is not quite identical, just shows as regular band and blind element, i.e. heterogeneity phenomenon on image.Heteropical appearance has produced very large impact to picture quality, and then has affected follow-up image applications.Therefore, the heterogeneity of detector is one of imaging system major issue that need to solve always.General employing is multinomial is fitting process, carry out Nonuniformity Correction based on methods such as statistic laws, eliminates or weakens heterogeneity phenomenon, is convenient to follow-up data processing.For multi-thread row moveout scan image, except will eliminating the heterogeneity of each alignment image, also to reduce the different and gray scale difference that causes of Whole Response between alignment image as far as possible, thereby be convenient to the processing such as follow-up frame matching.

Summary of the invention

The object of this invention is to provide a kind of asymmetric correction method that is applicable to the sub-pixel composograph of multi-thread row moveout scan, solve the heterogeneity phenomenon problem of multi-thread row image, eliminate overall intensity between alignment image poor simultaneously.

Technical solution of the present invention is: a kind of multi-thread row moveout scan subpixel image nonuniformity correction method, and step is as follows:

(1) construct multi-thread row moveout scan sniffer, this device comprises optical system, scanning mechanism and multi-thread row detector; Described scanning mechanism comprises pendulum mirror and drive shaft thereof; Described multi-thread row detector is two detector array, and detector array adopts N _tindividual detection array composition, the instantaneous field of view that pixel is corresponding is IFOV, adjacent two detection arrays are arranged in parallel, at the vertical scanning direction 1/N that staggers successively _tindividual pixel, and the detection array S that samples in direction of scanning, in a sampling length is set _tinferior; Described sampling length is the instantaneous field of view that pixel is corresponding; Described N _tbe more than or equal to 2; Described S _tspan is S _t>=2;

(2) optical system images in focal plane by scene in visual field together with scanning mechanism, drive shaft drives the rotation of pendulum mirror, scene imaging in linear field is with tandem two detector array on the inswept focal plane of certain speed, two detector array are to successively imaging of same position scene in visual field, imaging time interval be the N in each detector array _tthe imaging simultaneously of individual detection array, obtains N _tgroup view data; Proceed to immediately afterwards step (3); Each detector array carries out scanning imagery according to the sampling interval that sampling number is corresponding is set in step (1) in direction of scanning, each imaging obtains respectively N _tgroup view data, obtains proceeding to immediately step (3) after data;

(3) respectively by the N of two detector array _tgroup view data is alignd after splicing is processed and is formed a frame detection image;

(4) on direction of scanning, complete after default sampling number, the frame detection image that each detector array correspondence is obtained spliced and obtains two width subpixel images according to the time;

(5) two width subpixel images are intersected to splicing by row, form the new stitching image I of a width _p1;

(6) to stitching image I _p1each row image carry out respectively following processing, all row obtain row to the image I after nonuniformity correction after finishing dealing with _p2;

(6.1) obtain I _p1each row image I _istatistic histogram H _i;

(6.2) for I _p1in each row image I _i, according to I _iand neighborhood N _mthe histogram of row image, calculates Gauss's weighting and expects histogram H _gi;

(6.3) according to H _iand H _gito I _icarry out histogram specification conversion;

(7) according to the order of the row intersection splicing of two width images in step (5), from I _p2middlely extract respectively corresponding row image, rebuild two width and complete the subpixel image of row to Nonuniformity Correction;

(8) by complete row to two width subpixel images after nonuniformity correction by same direction half-twist respectively, repeating step (5)～(6), obtain proofreading and correct rear image I _p3;

(9) according to the order of the row intersection splicing of two width images in step (5), from I _p3middlely extract respectively corresponding row image, rebuild two width and complete the subpixel image of row to nonuniformity correction;

(10) by completing the capable two width subpixel images to nonuniformity correction by 90 ° of the opposite spins of step (8) rotation, two width subpixel images of row, column both direction nonuniformity correction have been obtained.

The present invention's advantage is compared with prior art:

(1) this method is considered the Fringe Characteristics of noise, and image is processed by column, has considered when prostatitis and six neighborhood row half-tone informations around.For the feature of fringes noise, the mode that adopts row to divide is carried out Local treatment to image, aspect hardware realizes, and in order to improve processing speed, can parallel processing.

(2) because the explorer response of multi-thread row detector is inconsistent, cause two images that alignment becomes to exist overall intensity poor, after this method is processed, can effectively reduce the gray scale difference between alignment image, make multi-thread row image in same tonal range, be conducive to improve the precision of subsequent treatment.

(3) method that the present invention proposes can be used for the Nonuniformity Correction of any two alignments in multi-thread scanning imaging system or multiple alignment images.

Brief description of the drawings

Fig. 1,2 is two kinds of mode schematic diagram of the multi-thread row moveout scan of the present invention sniffer;

Fig. 3 is that schematic diagram is processed in detector array two field picture splicing of the present invention;

Fig. 4 is that schematic diagram is processed in the splicing of the sub-pixel row of multi-thread row moveout scan two width of the present invention intersection;

Embodiment

Below in conjunction with accompanying drawing and example, the present invention is elaborated.A kind of multi-thread row moveout scan subpixel image nonuniformity correction method, step is as follows:

(1) construct multi-thread row moveout scan sniffer, this device comprises optical system 1, scanning mechanism 2 and multi-thread row detector 3; Described Scan Architecture comprises pendulum mirror and drive shaft thereof; Described multi-thread row detector is two detector array, and detector array adopts N _tindividual detection array composition, the instantaneous field of view that pixel is corresponding is IFOV, adjacent two detection arrays are arranged in parallel, at the vertical scanning direction 1/N that staggers successively _tindividual pixel, and the detection array S that samples in direction of scanning, in a sampling length is set _tinferior; Described sampling length is the instantaneous field of view that pixel is corresponding; The angular scanning speed of described multi-thread row moveout scan sniffer scanning mechanism is wherein distance d between two detector array, the target minimum movement speed v of detection _min, optical system focal distance f, the ground sampled distance GSD of detector array; Described N _tbe more than or equal to 2; Described S _tspan is S _t>=2; Below with N _t=2 describe for example.

What Fig. 1 provided is front end scanning probe device; The incident light of the emittance information that comprises target and background converges to focal plane through optical system 1 after the reflection of pendulum mirror, forms the picture of scenery, and drive shaft drives pendulum mirror according to default angular speed rotation, makes picture inswept each detector array successively of scenery.When the picture of scenery is during with inswept one of them detector array of certain speed, detector is sampled to the picture of scenery.What Fig. 2 provided is rear-end scanning sniffer.The incident light of the emittance information that comprises target and background converges to pendulum mirror through optical system 1, reflexes to focal plane through pendulum mirror, forms the picture of scenery.Drive shaft drives pendulum mirror according to default angular speed rotation, makes picture inswept each detector array successively of scenery.When the picture of scenery is during with inswept one of them detector array of certain speed, detector is sampled to the picture of scenery.

In this example, optical system 1 is the optical system of typical Cassegrain form, formed by primary mirror and secondary mirror, incident ray through primary mirror and secondary mirror reflection after converging, incide on detector array.

(2) optical system 1 together with scanning mechanism 2 by visual field in scene image in focal plane, drive shaft drives the rotation of pendulum mirror, scene imaging in linear field is with tandem two detector array on the inswept focal plane of certain speed, two detector array are to successively imaging of same position scene in visual field, imaging time interval be the N in each detector array _tthe imaging simultaneously of individual detection array, obtains N _tgroup view data; Obtain entering immediately step (3) after view data; In this simultaneously, each detector array still according in step (1), arrange in a sampling length sampling number, carry out scanning imagery in direction of scanning, each imaging obtains respectively N _tgroup view data, obtains proceeding to immediately step (3) after view data equally; For example, S can be set _t>=2, can realize the more than 2 times over-sampling of detector array on direction of scanning;

(3) respectively by the N of two detector array _tgroup view data is alignd after splicing is processed and is formed a frame detection image, and splicing is processed as shown in Figure 3, by N _tgroup pattern intersects splicing mutually.Processed and obtained sub-pixel frame detection image by splicing, realize target is in the stretching of vertical scanning direction.

(4), after default sampling number, the frame detection image that each detector array correspondence is obtained spliced and obtains two width subpixel images according to the time; Default desirable 200～300 row of sampling number, increase default sampling number and can increase scan image details, improve the precision of successive image processing; Reduce the efficiency that default sampling number can improve data processing, therefore default sampling number can regulate according to actual conditions.

(5) two width subpixel images are intersected to splicing by row, form the new stitching image I of a width _p1, the row of two width subpixel images intersect splicing processing as shown in Figure 4, and in figure, top is two width subpixel images, and below is spliced image;

(6) obtain I _p1the statistic histogram H of every row _i;

(7) for I _p1in each row image I _i, according to I _iand neighborhood N _mthe histogram of (general 8-12 row) row image, calculates Gauss's weighting and expects histogram H _gi, suc as formula (1),

$H_{\mathrm{Gi}}=\underset{j=-\mathrm{Nm}}{\overset{\mathrm{Nm}}{\mathrm{\Σ}}}g(\mathrm{\σ},j)\×H_{i+j}/(2N_m+1)---\left(1\right)$

H in formula (1) _giit is the expectation histogram of i row image; H _i+j, j ∈ [N _m, N _m] be I _p1in i row and N around thereof _mthe grey level histogram of neighborhood image; G (σ, j) is gaussian weighing function, can be calculated by formula (2):

$g(\mathrm{\σ},x)=\frac{1}{\mathrm{\σ}\sqrt{2\mathrm{\π}}}{e}^{\frac{{-x}^2}{2{\mathrm{\σ}}^2}}---\left(2\right)$

In formula (2), σ is Gaussian function standard deviation, and x is the distances of other image row to present image row;

(8) according to H _iand H _gito I _icarry out histogram specification conversion;

(9) by I _p1each row image repeating step (6)～(8), obtain row to the image I after nonuniformity correction _p2;

(10) according to the order of the row intersection splicing of two width images in step (5), from I _p2middlely extract respectively corresponding row image, rebuild two width and complete the subpixel image of row to Nonuniformity Correction;

(11) by complete row to two width subpixel images after nonuniformity correction by same direction half-twist respectively, repeating step (5)～(9), obtain proofreading and correct rear image I _p3;

(12) according to the order of the row intersection splicing of two width images in step (5), from I _p3middlely extract respectively corresponding row image, rebuild two width and complete the subpixel image of row to nonuniformity correction.

(13) by completing the capable two width subpixel images to nonuniformity correction by 90 ° of the opposite spins of step (11) rotation, two width subpixel images of row, column both direction nonuniformity correction have been obtained.

The unspecified part of the present invention belongs to general knowledge as well known to those skilled in the art.

Claims (1)

1. a multi-thread row moveout scan subpixel image nonuniformity correction method, is characterized in that step is as follows:

(1) construct multi-thread row moveout scan sniffer, this device comprises optical system, scanning mechanism and multi-thread row detector; Described scanning mechanism comprises pendulum mirror and drive shaft thereof; Described multi-thread row detector is two detector array, and detector array adopts N _tindividual detection array composition, the instantaneous field of view that pixel is corresponding is IFOV, adjacent two detection arrays are arranged in parallel, at the vertical scanning direction 1/N that staggers successively _tindividual pixel, and the detection array S that samples in direction of scanning, in a sampling length is set _tinferior; Described sampling length is the instantaneous field of view that pixel is corresponding; Described N _tbe more than or equal to 2; Described S _tspan is S _t>=2;

(2) optical system images in focal plane by scene in visual field together with scanning mechanism, drive shaft drives the rotation of pendulum mirror, scene imaging in linear field is with tandem two detector array on the inswept focal plane of certain speed, two detector array are to successively imaging of same position scene in visual field, imaging time interval be the N in each detector array _tthe imaging simultaneously of individual detection array, obtains N _tgroup view data; Proceed to immediately afterwards step (3); In this simultaneously, each detector array carries out scanning imagery according to the sampling interval that sampling number is corresponding is set in step (1) in direction of scanning, and each imaging obtains respectively N _tgroup view data, obtains proceeding to immediately step (3) after data;

(3) respectively by the N of two detector array _tgroup view data is alignd after splicing is processed and is formed a frame detection image;

(4) on direction of scanning, complete after default sampling number, the frame detection image that each detector array correspondence is obtained spliced and obtains two width subpixel images according to the time;

(5) two width subpixel images are intersected to splicing by row, form the new stitching image I of a width _p1;

(6) to stitching image I _p1each row image carry out respectively following processing, all row obtain row to the image I after nonuniformity correction after finishing dealing with _p2;

(6.1) obtain I _p1each row image I _istatistic histogram H _i;

(6.2) for I _p1in each row image I _i, according to I _iand neighborhood N _mthe histogram of row image, calculates Gauss's weighting and expects histogram H _gi;

(6.3) according to H _iand H _gito I _icarry out histogram specification conversion;

(7) according to the order of the row intersection splicing of two width images in step (5), from I _p2middlely extract respectively corresponding row image, rebuild two width and complete the subpixel image of row to Nonuniformity Correction;

(8) by complete row to two width subpixel images after nonuniformity correction by same direction half-twist respectively, repeating step (5)～(6), obtain proofreading and correct rear image I _p3;

(9) according to the order of the row intersection splicing of two width images in step (5), from I _p3middlely extract respectively corresponding row image, rebuild two width and complete the subpixel image of row to nonuniformity correction;

(10) by completing the capable two width subpixel images to nonuniformity correction by 90 ° of the opposite spins of step (8) rotation, two width subpixel images of row, column both direction nonuniformity correction have been obtained.